Table 1.

Estimation of tumor-initiating cell frequency of hypoxia-inducible factor-1α wild-type and knockout mammary tumor epithelial cells^a

	MTEC genotype
Estimated cell frequency	HIF-1α WT tumor-positive	HIF-1α-KO tumor-negative	HIF-1α WT	HIF-1α-KO	P valuesb
Number of cells injected, % (n)
500	78% (7 of 9)	0% (0 of 8)			0.0023
200	90% (9 of 10)	10% (1 of 10)			0.0011
100	77% (10 of 13)	9% (1 of 11)			0.0003
50	69% (11 of 16)	6% (1 of 16)			0.0006
25	30% (6 of 20)	0% (0 of 20)			0.0202
10	35% (8 of 23)	0% (0 of 22)			0.0038
Estimated TIC frequency by ELDA (95% CI)			1 of 82 (1 of 57 to 1 of 117)	1 of 2,915 (1 of 925 to 1 of 9,193)	5.79e-21

^aELDA, Extreme Limiting Dilution Analysis; HIF-1α, hypoxia-inducible factor 1α; KO, knockout; MTEC, mammary tumor epithelial cell; TIC, tumor-infiltrating cell; WT, wild type. Frequency of tumors following limiting dilution transplantation of WT or KO MTECs is shown. The number of tumor-positive recipients per the total number of recipients at day 36 posttransplant and the P-values between genotypes for each cell density tested are listed. The estimated frequency of TICs was determined using the publicly available ELDA software. ^bP values were calculated using Fisher's exact test.